The major goal of this project is to develop broadly reactive and potent human and rhesus monkey monoclonal antibodies (HMAbs and RhMAbs) recognizing quaternary neutralization epitopes (QNE). This group of epitopes has only very recently received attention, mainly because suitable methods for detecting such antibodies were not previously available. It is now feasible to identify patients whose sera contain this novel class of antibody. MAbs reflecting immune responses to QNEs will be required to precisely define their structure(s). In this project, we will use improved methodologies generating human and rhesus MAbs recognizing QNEs that will contribute critically important reagents for understanding QNE structure and function. Human studies will involve CAPRISA cohort patients, such as CAP256, a South African patient with high titers against QNEs of subtype C isolates, as well as U.S. patients studied in the Pinter lab. Likewise, we will produce monkey MAbs from macaques making QNE directed antibodies as a result of infection with SHIVs expressing conserved VIA/2 determinants of QNEs. MAbs will be used in mapping epitopes and structural analysis of QNEs. This project will involve intense collaborative interactions with all the individual Projects and Cores.